Radio apparatus



July 14, 1936. G, UNDER 2,047,930

RADIO APPARATUS Filed Aug. 51, 1933 s Sheets-Shet 1 .Fgii.

I/VVE/VTOEI m 14.1 Ernest GLindei; sou/e05 4 n 1 75 JB pull #mwq/R July 14, 1936. E. G. LINDER RADIO APPARATUS Filed Aug. 31, 1933 3 Sheets-Sheet 2 IN VE/V me Ernest GCLzIndw;

,5) Ms Arrow 14 Patented July 14, 1936 UNH'E'ED STATES ATENT orrics RADIO APPARATUS Application August 31, 1933, Serial No. 687,544

24 Claims.

My invention relates to radio apparatus and particularly to means for modulating and demodulating radio energy having a short wave length.

While there are many advantages in the use of such radio energy, it is difficult to modulate it to the desired degree without changing its wave length. In other words, instead of obtaining a pure amplitude modulation, both amplitude and frequency modulation are obtained.

It is also difdcult to receive radio energy having a very short wave length because a slight variation in the frequency of the received energy prevents the energy from passing through the tuned circuit of the receiver.

It has been hscovered that the difiiculty in modulating such energy can be overcome by intercepting the path of the radio waves by means of a device which is electrically independent of the high frequency generator and by varying the electrical or mechanical characteristics, or both, of this device in accordance with a signal. Such a system is described and claimed in a copending application of Irving Wolff, Ser. No. 687,599 filed :25 August 31, 1933, and assigned to the same assignee as this application.

An object of my invention is to provide an improved method and means for modulating high frequency radio energy in a system of the abovementioned type.

More specifically, an object of my invention is to provide an improved method and means for providing a high percentage of modulation of radio energy at 'very short wave lengths Without producing frequency variations therein.

A further object of my invention is to provide means for transmitting a sharp beam of modulated radio energy.

A still further object of my invention is to provide an improved receiving device for high frequency radio energy.

In practicing my invention, I improve upon the system disclosed in the above-mentioned Wolff application by interposing a region of free. electric charges in the path of a radio wave and controlling a condition of said region in accordance with a signal, whereby the radio wave is modulated. Specifically, I prefer to interpose a region of ionized gas in the path of the radio Wave and to vary the degree or character of ionization in accordance with a signal.

I also avoid the use of a tuned. receiver circuit and the consequent difiiculty in tuning by utilizing an electric discharge device positioned at the receiver in the path of an incoming signal.

Other features and advantages of my invention will appear from the following description when taken in connection with the accompany- 5 ing drawings in which Figures 1 to '7 are schematic diagrams of embodiments of my invention utilizing a beam of radio energy;

Fig. 8 is a schematic diagram of another em- 10 bodiment of my invention in which the radio energy is broadcast instead of being concentrated into a beam;

Fig. 9 is a schematic diagram of a modified form of the invention as illustrated in Fig. 8;

Figs. 10 to 17 are views showing various forms of modulating devices which may be utilized in practicing my invention; and

Fig. 18 is a curve showing the selective absorption characteristic of the gases preferably 20 utilized in certain of said modulation devices.

The embodiment of the invention illustrated in Fig. 1 comprises a high frequency generator I, such as a magnetron'oscillator, electrically connected to a dipole antenna 3 located inside a parabolic reflector 5. The energy radiated by the antenna 3 is directed into the form of a beam by the reflector 5 and is transmitted to a receiving reflector l which has a dipole antenna 9 located therein and connected to a radio re ceiver ll.

In the past it has been customary to signal over such a radio beam by modulating the high frequency energy at the generator itself, in which case the modulated radio energy is impressed upon the transmitting antenna. It is difficult to obtain a'radio beam of constant low wave length having amplitude modulation, for the reason that it has been found in practice that the modulating device at the generator may cause the frequency of the generator output wave to change.

In accordance with the above-mentioned embodiment of my invention, I pass the radio beam through the electric discharge of a modulating device l2 positioned in the path of the radio beam and electrically independent of the high frequencygenerator. This device comprises an envelope l3 filled with a gas, such as one of the noble gases, which can readily be ionized;

Electrodes l5 and I! are positioned inside the envelope l3 and are connected to a source of ionizing potential l9 through a resistor 2| and the secondary 23 of an audio or modulation signal frequency transformer 25, the resistor 2! be- 5 ing provided to limit the flow of current through the ionized gas. The primary 2'! of the audio frequency transformer 25 is connected to the source of modulating current which is indicated on the drawings as being an audio frequency source.

By means of this circuit, the gas in the envelope I3 is maintained constantly ionized by the direct current potential of source I 9, while the degree of ionization is varied in accordance with the modulating voltage appearing across the secondary 23. I have found that such a device will produce an undistorted modulated radio beam at the receiver. For example, if voice currents are put through the primary 21, the voice can be heard at the receiver in its original undistorted-form.

The modulating device I2 maybe positioned to intercept the radio beam at any point, although obviously the preferred position is relatively close to the transmitter reflector 5. If desired,'the envelope may be placed inside the transmitter refiector, itself. V

The modulating effect caused by the ionized gas is due to various properties of the gas. The modulating voltage varies the density and distribution of ionization within the envelope and hence the electrical and optical properties of the gas, such as dielectric constant, conductivity, coeflicient of absorption, coefficient of reflection, diffuse scattering, temperature, etc.

The above described apparatus provides substantially pure amplitude modulation. 'The stability of the transmitter is much better than that of the usual short wave transmitter since the oscillating circuit of the generator is not seriously interferred with. In fact, the'only interference with the oscillating circuit is that produced by the small amount of energy which may be reflected from the ionized gas back into the reflector. This reflected energy may vary the load on the antenna slightly. v

Where a plane of ionized gas is utilized for modulating, the energy reflected therefrom may be prevented from reaching the transmitter reflector by setting the modulating reflector at an angle to the axis of the radio beam, as explained in the above-identified Wolff application.

A further advantage inherent in this type of system is that a radio beam of greater intensity can -be obtained from a given oscillator, since the oscillator may be adjusted for maximum output without regard to where the operating point lies on the characteristic curve of the oscillator. That is, the oscillator and modulator adjustments are independent of each other.

If desired, in the system shown in Fig. 1, amplitude modulation may be put on the beam at the generator I in a conventional manner and this modulation addedto the modulation pro duced by the tube [2, care being taken to keep the two modulations in phase. I

In Fig. 2- are shown both my improved receiver and a modification of the modulating device illustrated in Fig. 1, The modulating device 29 comprises a spherical envelope 3| containing gas which may be ionized by a suitable potential across two electrodes 33 and 35. In this modification the electrode 33 is a metallic ring which is coated on the inside of the envelope 3|. The electrode 35 is a conductor extending through the center of the ring electrode 33 and normal to its plane. A steady ionizing potential is applied to the electrodes 33 and 35 from a suitable direct current source such as a battery 31, through a current limiting resistor 39.

The modulating voltage is impressed upon the electrodes 33 and 35 by means of an audio frequency transformer 4| connected to the electrodes through a conductor 43 and a blocking condenser 45.

The general effect of the modulating device 29 is the same as that of the device l2 shown in Fig. 1. It will, however, produce one additional effect upon the beam since it is designed to act as a diverging lens when the ring electrode is negative. The .amount that the beam is caused 'to diverge is dependent upon either the degree or distribution of ionization of the gas, or both. It

follows, therefore, that even if the other properties of the'gas, mentioned above, were unchanged, the device would modulate the beam solely by the lens action. If desired, the modulating device 29 may be employed with the specific form of modulating circuit shown in Fig. 1.

.The electric lens 29 is described and claimed in application Serial No. 687,575,- filed August-3l, 1933, inthe name of Vladimir K. Zworykin.

The receiving apparatus illustrated in Fig. 2 includes a gas-filled tube 39 positioned at or near the principal focus of a parabolic reflector32. Preferably, the tube 39 is placed at the principal focus of the reflector 32 although this exact position is not essential for satisfactory operation. The tube 30 comprises an envelope 34 filled with a gas, such as neon, which can be readily ionized by means of a voltage applied across two electrodes 36 and 38 mounted in the'envelope 34.

Two conductors 49 and 42 serve both as a support for thetube 30 and as means for connecting the electrodes 36 and 38 to a source of ionizing potential 44 through a resistor 46 and the primary winding 48 of an audio-frequency transformer 50. The transformer 59 transfers the current variations of the tube'circuit to an audiofrequency amplifier 52 which has a loud speaker 54 connected to its output circuit.

The present theory of operation of my receiver is based upon the apparently correct assumption that the modulated radio beam varies the degrees of ionization of the-gas in tube 30. Since the degree of ionization varies in accordance with the amplitude of the received energy, the current transferred to the audio amplifier 52 will correspond to said variations in amplitude. That is,

the audio amplifier output will correspond to the modulation on the radio beam.

. The degree of ionization of the gas in tube 30. probably is varied by the passage of the radio beam through the gas. It'may be, however, that the received beam sets up varying potentials on the electrodes, and that these potentials cause the change in ionization.

In the embodiment shown in Fig. 3, the receiving and transmitting apparatus of Fig. l is shown in connection with a modulating means in which the ionized gas device 47 has two electrodes 49' and so arranged that aplane :of ionized gas is formed inside the envelope 53. The plane of the ionized gas coincides with the plane of the electrode 49. Preferably the spacing between the grid wires 55 of the electrode 49 is small in cornparison with the wave length of the radio beam, and the gas pressure is such that the Crookes dark space is small in comparison with the spacing between the grid wires 55'. 7

Ionization may be maintained by means of current having a super-audible frequency. A super-audible frequency generator indicated at 51 is connected to a modulator 59 which may be of any of the well known designs. The modulatlng frequency may be supplied from a microphone 6| connected to the modulator 59. If desired, the ionizing and modulating potentials may be applied to the electrodes 49 and 5i by means of either the circuit shown in Fig. 1 or the circuit shown in Fig. 2, in which case the electrode 49 is negative, being connected to the negative terminal of the direct current source.

When using a grid composed of wires as one electrode, as illustrated in Fig. 3, certain precautions must be taken to insure proper operation of the device. It is well known that a transmitter of the type shown generates a radio beam which is strongly polarized in the plane of the dipole antenna 3, for example, in a vertical plane. Since the grid wires 55 are spaced closer together than one wave length, they will act as a reflector, substantially the same as a solid sheet of metal, if they are placed so that they run parallel to the plane of polarization. This difliculty can be avoided by so placing the electrode 49 that the closely spaced wires 55 are perpendicular to the plane of polarization, or in the example given, placed so they are horizontal.

If desired, a third electrode may be employed for varying the degree of ionization of a modulating device 63 as illustrated in Fig. 4. The transmitter and receiver of Fig. 1 are shown in connection with a further modification of modulator means. In this arrangement, a constant ionizing potential is impressed across electrodes 65 and 61 through a resistor 69, while the modulating voltage is impressed upon a control grid H through an audio frequency transformer 13 shunted by a resistor 15. Preferably, the control grid TI is negatively biased with respect to the anode 65, as by means of a battery Tl.

While the degree of control of the ionized gas discharge obtained by means of the control grid 1| will not be very great, it will be suflicient for modulating the radio beam, especially if the control grid H is placed in the Crookes dark space.

In the form of my invention illustrated in Fig. 5, the ionized gas modulating device 19 is shaped in the form of a prism so that the radio beam will be bent as it passes through the prism. Its construction will hereinafter be explained. The amount of bending will depend upon the degree of ionization of the gas, and may be controlled by means of the modulating circuit illustrated, which is the same as the circuit shown in Fig. 1, or, if preferred, by means of the circuits shown in Figs. 2 and 3.

In order to obtain undistorted modulation by means of the system shown in Fig. 5, the receiving reflector I should be placed in a certain definite location with respect to the energy distribution in the radio beam which is in the form of a cone. The energy distribution in the beam is indicated by the curve 8!. It will be noted that the amount of energy is greatest at the center of the cone and that at each side of the center of the cone there is a portion of the curve between the points A and B which is substantially a straight line. It is desirable to have the portion of the beam corresponding to this straight line portion swing back and forth in front of the receiving reflector E. This will be accomplished if the center line of the cone is swung between the limits indicated on the drawings.

The prism used in the system of Fig. 5 may be constructed in various ways. One form of construction is shown in Fig. 11 to which attention is directed, along with Fig. 5. This prism may comprise a single long tube 83 which isbent back and forth upon itself and shaped in the form of a prism. The tube is filled with a gas such as neon, for example, which can be ionized by means of two electrodes 85 and 81, one at each end of the tube 83.

When the length of the radio beam is such that the reflector 5 must be relatively large in comparison with glass envelopes which can at present be made readily, it may be desirable to so design the reflector 5 that the beam is focused by the reflector as shown in Fig. 6. This permits the use of a smaller envelope 89 for the free electric charges, since it may be placed at or near the principal focus of the reflector 5 where the crosssection of the radio beam is small. After the beam passes through the device 89, its rays may be made substantially parallel by means of a lens 9! so that the beam can be directed to a remote receiving reflector I. As illustrated, the device 89 may comprise a hot cathode, a control grid, and an anode for producing a plane of pure electron discharge in the path of and at right angles to the radio beam. By varying the potential on the control grid and thus varying the intensity of the discharge, between the cathode and anode, the radio beam may be modulated.

In Fig. 7, there is illustrated an embodiment of my invention which makes possible the transmission of a sharply defined modulated beam of radio energy. When forming a beam of radio energy even at wave lengths of a few centimeters, it is difiicult to obtain a beam of small cross-section which is sharply defined since the wave length is not extremely small in comparison with the reflector dimensions as in the case of light.

In the apparatus shown in Fig. '7, the reflector, indicated at 99, is made large enough to sharply define the energy radiated from the dipole antenna 92. The resulting beam necessarily has a fairly large cross-section so that the location of the receiving reflector need not be very exact to receive part of the beam. This may be undesirable in some instances, as in the case of secret signaling.

Therefore, instead of modulating the entire beam, I position one of my ionized gas modulating devices 94 in the path of a portion of the radio beam. The device 94 will cast a modulated shadow which will be smaller in cross-section than the beam itself and will, in effect, give a sharper radio beam.

The device 94 is of a type which modulates by absorption, reflection, and/or scattering, that is, it should not be a type which disperses the beam. The device 94 illustrated in Fig. 1 is shown in detail in Fig. 10. It comprises a long gas filled tube 95 bent back and forth upon itself to form a rectangular grid. Electrodes S! and 99 are provided at each end of the tube 95 by means of which the gas may be ionized. The spacing between adjacent portions of the tube 95 should preferably be relatively close and in any case less than one wave length of the radio beam.

Instead of the device shown in Fig. 19, either the one shown in Fig. 3 or the one shown in Fig. 13 (and described hereinafter) may be utilized.

My'invention is not restricted to beam transmission systems, but may be applied to transmitting systems in which the radio energy is radiated in all directions. For example, as illustrated in Fig. 8, a dipole antenna 96 mounted upon a non-conducting mast 98 may be surrounded completely by ionized gas enclosed in a long glass tube "H. In this arrangement, the high frequency generator I03 connected to the antenna V velope IUI. not located in the ionized gas, so that itis in i1 circuits.

may, for example, generate energy having a wave is connected to a microphone II9 through a potential source or battery I2I.

Instead of a dipole antenna, one of the type illustrated in Fig. 9 may beenclosed by the en- In Fig. 9, however, the antenna is contact with the gas, but is surrounded by ahelical tube of ionized gas which may be wound as. shown, or otherwise disposed around the antenna. In this arrangement, electrodes indicated at I23 and I25 at the ends of the gas filled tube I27 are connectedto a modulating circuit,

which is the same as the one shown in Fig. 8.

Radio energy may be supplied to the antenna 528 by means of any of the well known coupling of the antenna IE8 is connected to the upper end of an inductance coil I29 which has its lower ,the conductor I60.

end connected to one terminal of a condenser ISI, the other terminal of condenser I3I being connected to ground. A transmission line I33 ed may be utilized. Some examples of such variations are illustrated in Figs. 12 to 1'1. Fig. 12 illustrates a form of tube which may b substituted for the tubes I2 and 26 shown in Figs;

1 and 2, and comprises a gas filled envelope I31 having a cylindrical electrode I39 and a rod-likeelectrode I 4| concentric with the cylinder I39. When employed for modulation purposes, the tube is preferably positioned with the electrode I4! parallel to the axis of the radio beam.

Fig. 13 illustrates another electrode arrangement for obtaining a plane of ionized gas. This device comprises a gas filled envelope I43 in which electrodes I45 and I4! have interleaving elements I 58 and .I5I, respectively. The elements I49 and I5I may be in the form of rods, all positioned in the same plane. It is apparent that with this structure, the plane of ionized gas coincides with the plane of the electrodes I45 and I41.

The ionization of the gas in a modulating device may be obtained by the use of either an external coil I53, as shown in Fig. 14, or external electrodes I55, as shown in Fig. 15, and the use of a high frequency ionizing potential. The tubes shown in Figs. 14 and may be substituted for the tube 4'! shown in Fig. 3 and satisfactory modulation of the radio beam obtained, providing a high frequency source, such as a radio frequency source, is substituted for the super-audible frequency source 51.

In Fig. 16 there is illustrated an arrangement in which a dipole antenna I51 is enclosed in a gas filled envelope I59 to form one of the ioniz lng electrodes. The other electrode is indicated at I6I. When using this device, the ionizing and modulating potentials may be impressed across the electrodes I51 and I6I by a circuit like the one shown in Fig. 1. The connection to the antenna electrode I5! is made at a voltage node on If a radio beam is to be radio beam.

In the circuit illustrated, the lower end a pure electrondischarge, up to the highest prestransmitted, the envelope I59 will be positioned at the proper point inside a reflector.

Fig. 17 illustrates a device for modulating radio'beam by reflecting the beam a variable amount. The gas filled envelope I63 contains a cathode'l65 in theform of a wire grid or grating, which may be either plane or curved, and an anode I61. If the proper potential is impressed across the electrodes I65 and IS], a layer of ionized gas will form along the surface of the l cathode I65. This ionized plane of gas will re-' flect a certainpercentage of the energy in a The reflecting property of the plane of gas may be utilized in a communication sys- .tem by positioning the receiver in the path of 1 the reflected beam. As the reflecting ability of the gas layer is varied by the variation in ionization, the amount of reflected energy which reaches the receiver will vary in accordance with the variation in voltage applied'to electrodes I65 gas of a modulating tube by means of ultraviolet light, Xrays,' heat, or any combination of these.

The nature of the gas employed in the various modulating devices described may vary widely. Either pure gases or gas mixtures may be employed, but preferably noblegases are used. The I gas pressure may vary from zero, where there is sure at whicha discharge can be produced. It will be understood that the pressure of the gas in tubes such as the ones shown in Figs. 1, 2

and 10 should be such that a uniform glow. or region of ionization fills the greater part of the envelope. In general, this pressure will be less than the pressure in tubes such as 53 and I43, shown in Figs. 3 and 13, respectively, where the fiow is to be confined to the region of an electrode.

Since some ionized gases show selective absorption for certain wave lengths due to plasma oscillations of electrons or ions, greater efficiency of modulation and demodulation may be obtained by operating near or at such absorption band. Fig. ,18 shows how one of my modulating devices operating in the neighborhood of an absorption band (the device shown in Fig. l, for example), will absorb the radio beam as the current through the modulating device is changed.

It is well known that certain gases exhibit a resonant reflect which causes them to absorb a comparatively large amount of energy having a Wave length corresponding tothe resonant point of the gas. Assume that a radio beam of a certain wave length is impressed'upon one of my gas modulating devices as shown in Fig. 1, Fig. 2, or Fig, 3, for example. If the gas pressure is made the proper value, the current through the modulating device can be increased until the gas absorbs the beam the maximum amount, that is, a resonant peak is obtained.

This resonant effect may be utilized in modulating the beam'by adjusting the current through 7 the modulating device until the point :0 on the curve is reached. The modulation then varies the modulating tube current about the point a: so that theabsorption of the radio beam is varied between the limits 1 and z. y

The selective absorption efiect may be utilized also with the demodulator shown in Fig. 2. In utilizing this effect, the unmodulated radio beam will be directed into the receiving reflector 32 and the current through tube 34 brought to a value (as by adjusting resistor 46) corresponding to the point a: on the curve shown in Fig. 18. With such an adjustment, variations in the radio beamintensity (amplitude modulations) will produce comparatively large variations in the current flowing through tube 34.

It will be apparent that various other modifications may be made in my invention Without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are necessitated by the prior art and are imposed by the appended claims.

I claim as-my invention:

1. The method of signaling which comprises generating and transmitting electromagnetic radio frequency energy in'the form of a beam, creating a region containing free electric charges in the path of said beam, and varying the ionization of said region in accordance with a signal.

2. The method of signaling which comprises generating and transmitting electromagnetic energy of radio frequency in the form of a beam, creating a region of ionized gas in the path of said beam, and varying the degree of ionization of said gas in accordance with a signal.

3. The method of signaling which comprises generating and transmitting electromagnetic energy of radio frequency in the form of a beam, creating a region of ionized gas in the path of said energy, varying the degree of ionization of said gas in accordance with a signal, and absorbing energy from said transmitted radio frequency energy.

4. In a radio system, means for generating electric energy of a high radio frequency, means for radiating said energy, and means including an electronic discharge device positioned in the path of the radiated energy for modulating said energy in accordance with a signal after said energy has been radiated.

5. In a radio system, means for generating electric energy of a high radio frequency, means for radiating said energy, means providing a region containing free electric charges for intercepting said radiated energy, and means for varying the ionization of said region in accordance with a signal.

6. In a signaling system, means for generating and transmitting a beam of radio frequency electric energy, and means including an electronic discharge device positioned in the path of said beam for modulating it in accordance With a signal.

7. In a radio system, means for generating and transmitting radio frequency electric energy, a

modulating device positioned in the path of said radiated energy, said device comprising a gasfilled envelope, means for ionizing said gas, and. means for varying the ionization of said gas in accordance with a signal.

8. Electrical apparatus comprising means for generating electric energy at a high radio frequency, means for transmitting said energy in the form of a beam, an ionized gas device so positioned that it intercepts said beam and means including said device for modulating said beam inaccordance with a signal.

9. Electrical apparatus comprising means for 3',

tioned'to intercept said beam, means for ionizing said gas, and means for varying the degree of ionization of said gas in accordance with signals. 11. Electrical apparatus comprising means for generating electric energy at a high radio frequency, means for transmitting said energy in the form of a beam, means for intercepting said beam by a confined gas, and means for controlling the ionization of said gas in accordance with a signal.

12. Electrical apparatus comprising means for generating electromagnetic energy at a high radio frequency, means for transmitting said energy in the form of a beam, means for intercepting said beam by an ionized confined gas, and means for controlling the electromagnetic energy absorbing properties of said ionized gas in accordance with a signal.

13. Electrical apparatus comprising means ior generating electromagnetic energy at a high radio frequency, means for transmitting said energy in the form of a beam, means for intercepting said beam by an ionized confined gas, and means for controlling the degree of ionization in accordance with a signal.

14. The method of signaling which comprises generating electromagnetic energy of a radio frequency, transmitting it in the form of a beam, creating a region of electric discharge positioned within the path of only a portion of said beam, and varying the ionization of said electric discharge in accordance with a signal whereby a modulated shadow of said beam is transmitted.

15. In a signaling system, means for generating electric energy of a radio frequency, means for concentrating said energy into the form of a beam, said second means comprising a reflector of dimensions large enough with respect to the wave length of said energy to produce a well defined beam, means for creating a region of electric discharge within the path of only a portion of said beam, and means for varying the electric energy absorbing properties of said electric discharge in accordance with a signal whereby a modulated shadow of said beam is transmitted.

16. In a signaling system, means for generating electric energy of a radio frequency, means for concentrating said energy into the form of a beam, said second means comprising a reflector of dimensions large enough with respect to the wave length of said energy to produce a well defined beam, means for creating a plane of ionized gas approximately normal to the axis of said beam and positioned within the path of only a portion of said beam, and means for varying the ionization of said gas in accordance with a signal whereby a modulated shadow of said beam is transmitted.

17. In combination, means for radiating a beam of electric energy of radio frequency, an electric discharge device positioned in the path of said beam for modulating :said beam, and means comprising a control electrode in said device for controlling said discharge in accordance trode, means for impressing an ionizing potential across said main electrodes, and means for impressing a modulating potential upon said grid.

19. In combination, means for radiating a V beam of electric energy of radio frequency, a modulating .device positioned in the path of said beam, said device comprising means for confining gas in the shape of a prism, means for ionizing said gas whereby said radio beam is refracted, and means for varying the ionization of said gas in accordance with a signal. r

20. In combination, means for radiating a beam of electric energy of radio frequency, re ceiving means for intercepting a portionof said beam, and means consisting of a confined gas for swinging the axis of said beam in accordance with a signal.

21. In combination, means for radiating a beam of electric energy of radio frequency, having a field strength distribution which is approximately linear over a certain region, receiving gas, said voltage having cordance with signals.

.means :for interceptingv said beam within said region, andmeans including an'ionized gas for deflecting said beam in accordance with a'signal, thie limitsofdeflection being such that said receiving means always intercepts said beam within said region. a

' 22. In combination, means ,for; radiatingv a beam of electric energy ,of radio frequency, a modulating device positioned in the path of said beam, said device comprising a gas-filled envelope and means for impressing a signal-modulated voltage of superaudible frequency upon said a value sufficient to ionize said gas. a y

23. Electrical apparatus comprising means for generating electric energy at ahigh radio frequency, means for transmitting said energy in the form of a beam, a gas filled envelope positioned to intercept said beam, means for ionizing said gas, and means for varying the distribution of ionization of said gas in accordance with signals. 7 V

24. Electrical apparatus comprising means for generating electromagnetic energy at a high radio frequency, means for transmitting said energy in the form of a beam, a gas filled envelope positioned to intercept said beam, means for ionizing said gas, and means for varying the degree and distribution of ionization of said gas in ac- ERNEST G. LINDER. 

